Predicting Fate of the Contraceptive Pill in Wastewater Treatment and Discharge
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The risk of endocrine disrupters to humans and wildlife is to date poorly understood, although evidence of effects is now widespread. In understanding the risk, an important step is the determination of the partitioning, as well as chemical and biochemical transformation, of compounds in the environment, the water cycle and the food chain. This is a complex task and this paper is a first step towards estimating some of these factors from a largely theoretical approach. A chemical fate model is used to predict the fate of the contraceptive drug 17a-ethinylestradiol (EE2). The example of the contraceptive pill is chosen to follow the journey of the drug from human ingestion and excretion to treatment in a sewage treatment plant (STP) using fugacity-based fate models, followed by discharge into a receiving river and eventually into the estuary/sea. The model predicts how EE2 will partition into the different compartments during each stage of this journey and thereby infiltrate into the food chain. The results suggest that a person would have to ingest more than 30,000 portions of fish to consume an equivalent to a single average dose of the contraceptive pill. While this scenario is highly unlikely, the biochemical consequence of the contraceptive pill is greatly significant. Furthermore, there are many identified similarly estrogenic compounds in the environment while this study only considers one. Cumulative effects of such compounds as well as degradation into other potent compounds may be anticipated. An important message in this paper is the interrelation of wastewater effluent discharge and eventual human exposure of marginally degradable and lipophilic chemicals. While at present the main concerns regarding endocrine disrupters appear to be the fear of their occurrence in drinking water sources, it is clear that the domains of wastewater treatment and discharge, water supply and contamination of food should not be treated as separate issues. The model suggests that exposure from food (contaminated by effluent) may be much more significant than from drinking water.